Endoscopic bite block

ABSTRACT

An endoscopic bite block, with teeth position defining regions which guide the subject&#39;s teeth to grip the bite block in their natural position, with the teeth of the upper jaw positioned further out than the lower jaw teeth. These teeth position defining regions are also preferably curved to match the curved shape of the jaw. The upper and lower parts of the front plate of the bite block may also be positioned at different distances out, so that upper and lower lip regions both contact the front plate snuggly. The bite block may be used with separate oral/nasal cannulae, or may incorporate breath sampling or gas supply cannulae. A flexible flapped curtain at the outer end of the bite block may be provided to largely enclose the inner volume of the bite block to enable more accurate capnographic sampling under conditions of wide-open mouth breathing.

FIELD OF THE INVENTION

The present invention relates to the field of bite blocks for endoscopicuse, adapted to provide for optimum subject comfort and tolerance, andespecially such endoscopic bite blocks with incorporated gas sampling ordelivery cannulae or for use with separate cannulae.

BACKGROUND OF THE INVENTION

A bite block is a device commonly used during upper gastro-intestinalendoscopic procedures to facilitate passage of anesophago-gastro-duodenoscopy (EGD) endoscope. The purpose of the biteblock is to allow the physician to perform the procedure without thesubject interfering by biting and damaging the endoscope tubing insertedvia his mouth, whether voluntarily or involuntarily.

The upper gastro-intestinal endoscopic procedure itself, together withthe use of a bite block, is often highly uncomfortable for the subject.For this reason it is very common for the subject to be sedated duringthe procedure. The sedative helps the subject to tolerate the procedure,rather than to oppose it, thus enabling the doctor to perform theprocedure undisturbed.

Despite this, it is common for the subject to show opposition to theprocedure. The subject will often resist entry of the endoscope by notswallowing as requested and by tensing his or her muscles. The subjectwill also often oppose the placement of the bite block itself before theprocedure, and more commonly during the procedure because of involuntarymuscular reactions, by trying to manipulate it out of his or her mouthby means of the tongue or teeth.

Prior art bite blocks are generally characterized by a number ofstructural features:

1. A. tubular body or barrel whose internal lumen serves as the channelfor passage of the endoscope, and whose top and bottom outer surfacesserve as the surfaces upon which the subject's teeth bite. Thesesurfaces are generally flattened.

2. A wall centrally connected to the outer end of the tubular body,shaped such that it should lie comfortably outside and around thesubject's mouth. It is this wall that fulfils the double function ofproviding a general alignment direction to the tubular body and ofpreventing the bite block from falling into the mouth. The wall is alsoknown as the front plate.

3. A band connected to the bite block and used to strap the bite blockfirmly to the subject.

A number of bite blocks are described in the prior art, which addadditional features to the above-mentioned basic features. Theadditional features are generally directed to assisting the physician inperforming the endoscopic procedure with minimum interference from thesubject, by making it more difficult for the subject to oppose the biteblock, which generally means making it more difficult for the subject toeject the bite block from the mouth. Thus in U.S. Pat. No. 5,174,284 toF. W. Jackson for “Endoscopic bite block”, there is described a biteblock with, inter alia, (i) a tubular outer surface whose upper andlower walls are sloped towards each other in the direction of the frontplate, so that as the subject's teeth bite down on the surfaces, thebite block tends to move back into the mouth where it seats more firmly;and (ii) a tongue depressor, which firmly forces the tongue downwards asthe teeth compress against the upper and lower surfaces of the biteblock channel, keeping the tongue seated below the mouthguard, where itcannot struggle to push the block out of the mouth. Additionally, thebite block has rear teeth guards, which require the mouth to open verywide in order for the bite block to fall out. In U.S. Pat. No. 6,257,238to N. M. Meal), for “Bite block for upper gastrointestinal endoscopywith tongue depressor”, there is described another bite block with atongue depressor, though the tongue depressor is therein described aspreventing the tongue from covering the channel of the bite block, andblocking the subject's throat.

One of the physiological effects of the use of such bite blocks is thata sensation of oral immobility may be generated because of the way inwhich such bite blocks operate. The bite block may thus be uncomfortablefor the subject and may produce a feeling of being gagged even beforethe insertion of the endoscope itself Furthermore, large amounts ofsaliva are commonly produced during these procedures, and since onemethod of dealing with saliva is by manipulating it with the tongue,depressing the movement of the tongue may prevent the subject fromdealing with it, again causing the subject to have a choking feeling.This general physiological feeling may increase the subject oppositionto the procedure even more, thus negating the initial, intended purposeof the invention,

In addition to the problems associated with the comfort and ease of useof prior art endoscopic bite blocks, a further problem exists when suchprior art bite blocks are used together with breath sampling means, inparticular capnographic sampling, or gas delivery, such as oxygen. It iscommon in endoscopic procedures for the doctor to try to reduce theopposition of the subject to the procedure by administering sedatives.However, as with all sedation procedures, careful monitoring of thesubject must then be performed, usually on a continuous orsemi-continuous basis, to avoid the adverse affects of over-sedation,

It is well known that a sedated subject is vulnerable to episodes ofhypo-ventilation and apnea. The ability to adequately monitor and detectthese episodes is essential when potent sedatives are employed. Pulseoximetry, to determine the blood SpO₂ level, is routinely used duringthese procedures, and provides a sensitive and reliable estimate ofarterial blood oxygenation. While breathing room air, apnea causesarterial oxygen de-saturation and can thus be speedily detected by meansof pulse oximetry. However, when subjects receive supplemental oxygen,as is recommended during sedation where breathing may be suppressed,apnea-induced oxygen de-saturation would be delayed until hyper-capniaensued. For this reason, capnography, the continuous measurement ofcarbon dioxide in the breath, is generally recommended as a moreappropriate and direct means to monitor for hypo-ventilation and apnea.

During medical procedures other than upper gastro-intestinal endoscopythe sedated subject is easily monitored with a capnograph, whichcontinuously samples the subjects' breath. This is realized using anappropriate breath sampling cannula device connecting between thesubject and the capnograph. The cannula is appropriately positioned inclose proximity to the subject's nose, or nose and mouth. Thecapnograph, using a pump, continuously extracts breath from the subjectvia the cannula, to the capnograph sensor for analysis. One example ofsuch a sampling cannula device is described in U.S. Pat. No. 6,422,240to G. Levitsky et al, for “Oral/Nasal Cannula”, assigned to the assigneeof the present application, and herewith incorporated by reference inits entirety.

In the prior art, CO₂ sampling during upper gastro-intestinal endoscopy,and especially during long duration procedures performed under sedation,monitoring is often performed using a separate nasal or oral/nasalcannula in conjunction with the bite block. Concomitant use of prior artbite blocks and cannulae is often not an optimal solution, and thecapnographic performance may be noticeably affected. The generallyapplied method of using a prior art adjunct oral/nasal cannula with aprior art bite block, is to put on the oral/nasal cannula after the biteblock has been inserted, such that the oral prong sits outside of thefront plate of the bite block and is often mis-positioned or occluded bythe bite block, or is located directly in the path of the endoscope andconsequently pushed aside or even bent back when the endoscope isinserted. There is essentially “competition” for the use of thesubject's oral passage between the need for oral breath sampling and theneed for the passage of the endoscope, and since the endoscope procedureis the mission being undertaken, it generally prevails over the needs ofthe capnographic sampling.

The alternative use of a nasal sampling cannula, in an attempt toovercome this problem, is generally inadequate, since it is known thatduring upper gastro-intestinal endoscopic procedures, it is usual forthe subject to perform largely oral breathing alone, and theeffectiveness of the nasal sampling is much reduced. However, iforal/nasal sampling is performed in an attempt to overcome this problem,even if the oral sampling opening is placed in such a position so as notto interfere with the region required for the insertion and maneuveringof the Endoscope, the existence of majority oral exhalation still leadsto another problem when using prior art devices. When the subject'smouth is wide open, as it is during upper G-I endoscopy, the excessbreath pressure within the oral cavity is very small, and the exhaledbreath therefore becomes diluted with the inhaled air, and sampling isthus inaccurate.

For the delivery of supplementary oxygen during endoscopic procedures,there exist in the prior art, a number of combination bite block/oxygendelivery cannula devices, such as those described in U.S. Pat. No.5,273,032 to T. J. Borody, for “Oxygenating oral medical appliance” andin U.S. Pat. No. 5,513,634, to F. W. Jackson, for “Combination integralbite block airway and nasal cannula”, both herewith incorporated byreference, each in its entirety.

Both of these patents describe methods for delivering supplementaloxygen during upper gastro-intestinal endoscopy from a single,integrated device. Unlike the situation with carbon dioxide sampling,the use of a single device that integrates the bite block with oxygendelivery is mainly important for convenience, and is not mandated forproviding optimal performance. A standard, separate oxygen supply nasalcannula could readily be positioned so as to adequately provide oxygento the subject even when a separate bite block is in place. This is notthe case when a separate breath sampling cannula is used simultaneouslywith a separate prior art bite block, as explained above.

One possible disadvantage of the integrated device described in U.S.Pat. No. 5,273,032 is that the oxygen is delivered via two tunnels withends that do not reach the nasal cavities, but instead direct the oxygengas stream towards the nasal cavities. The ability of these devices toefficiently direct the oxygen gas stream to the nasal cavities is thusdependant on how well the bite block sits in its intended positionwithin the subject's mouth. Any tilt of the bite block inevitably causesa tilt in the direction of the nasal tunnels and consequently misdirectsthe oxygen gas stream away from the subject's nostrils. Such tilting ofprior art bite blocks, or of the combination bite block/cannula deviceof U.S. Pat. No. 5,273,032 is common, as described hereinabove, eitherbecause of a feeling of discomfort when the bite block is in the mouth,causing the subject to attempt to move it, or because of the tiltgenerated by the placement position of the teeth in such prior art biteblocks, as explained above. The integrated device described in U.S. Pat.No. 5,513,634, on the other hand, is equipped with nasal prongs of asoft material, that do reach the nostrils of the subject. However, evenwith this device, tilting of the bite block causes the prongs to hetilted also, and may consequently cause them to exit the nostrils. Thecorrect seating of the bite block is therefore likely to have an effectalso on the efficacy of oxygen delivery also.

There therefore exists a need for an endoscopic bite block which fitscomfortably into the mouth of the subject, without imposing anyunnatural constraints on the subject's oral position, and consequentlywhich reduces sensations in the subject that would cause the subject tooppose its presence. Furthermore, there exists a need for such anendoscopic bite block which enables accurate breath sampling, even inconditions of open mouth oral breathing, and which does not interferewith the endoscopic procedure.

The disclosures of each of the publications mentioned in this sectionand in other sections of the specification, are hereby incorporated byreference, each in its entirety.

SUMMARY OF THE INVENTION

The present invention seeks to provide a new endoscopic bite block,which overcomes some of the disadvantages of prior art bite blocks,related to a possible lack of comfort of such bite blocks when seated inthe subject's mouth, to the ability to deliver supplementary oxygenreliably and to sample the patient's breath effectively, and to theproblems of efficient wide-open mouth oral breath sampling. According toa first preferred embodiment of the present invention, the bite blockdiffers from prior art bite blocks in that means are provided on theouter upper and lower surfaces of the tubular body for ensuring that thesubject's teeth grip the bite block in the teeth's natural position,without the need for the subject to force his or her lower jaw into anuncomfortable position. Since the upper jaw tooth line is generallydisposed further out in the mouth than the lower jaw teeth, this ispreferably accomplished in the bite block of the present invention, byproviding means to ensure location of the top teeth further forward onthe tubular body than the bottom teeth, such as by provision of suitablylocated grooves or stepped regions in the outer surfaces to locate bothsets of teeth appropriately. These grooves or stepped regions are alsopreferably curved to match the curved shape of the human jaw.Consequently, even though the upper teeth are located further forwardthan, the lower teeth, it is found that because of the natural grippingposition of the teeth, use of the bite block of the present inventiondoes not result in the generation of moments which attempt to tilt thebite block out of its optimal location. This is in contrast to prior artbite blocks with teeth gripping positions aligned opposite each other,where, because of the forced unnatural position of the lower jaw, thebite block may tend to tilt under the action of spontaneous movements ofthe lower jaw to relieve the discomfort.

Furthermore, according to another preferred embodiment of the presentinvention, the front plate at the outer end of the bite block, whichshould lodge firmly against the lips of the subject, is preferablyshaped such that it is not set at a uniform distance at the outer end ofthe tubular body, but rather, the top region is set further out than thebottom section, such that the natural position of the subject's upperlip region, projecting further out from his or her face than the lowerlip region, does not prevent the front plate of the bite block fromsitting firmly against both sets of lips. Such positioning of the frontplate firmly against the whole of the subject's mouth also assists inovercoming any tendency for the bite block to tilt out of the subject'smouth because of moments generated should the subject move his teethfrom the optimal natural gripping position.

Additionally, according to yet another preferred embodiment of thepresent invention, the attaching points of the band for strapping thebite block round the back of the subject's head may be generally setabove the horizontal center line of the front plate, such that a momentis generated which tends to exert a stronger pull on the top section ofthe front plate than on the bottom section, such that the whole biteblock undergoes a moment which acts to counteract any undesired momentgenerated by the teeth of the subject.

The bite blocks of the present invention can also preferably be providedeither with built-in sampling and gas delivery passages, such that thebite block has an integrated capnographic cannula and oxygen deliverysystem, or as a bite block for use with a separate oral/nasal cannula.According to a further preferred embodiment of the present invention, anendoscopic bite block intended for use with a separate oral/nasalcannula is described, in which the oral sampling is performed by meansof an opening in the roof of the bite block central channel, with theend of the oral sampling prong of the cannula sitting on the innersurface of the front plate, closed between the plate and the patient'supper lip. The oral prong may preferably be inserted into this openingsuch that its tip just projects into the top of the channel, though thisis not essential. The oral prong of the cannula is thus able to operatewithout being disturbed by, and without disturbing, the insertion of theendoscopic probe through the bite block. A groove is also preferablyprovided in the top of the front plate to firmly locate the oral prongin its correct position between the subject's upper lip and the frontplate.

Furthermore, according to yet another preferred embodiment of thepresent invention, the cross sectional area of the bite block innerchannel is substantially closed off near its outer end by means of aflexible curtain, which maintains a generally closed inner volume forthe central channel of the bite block. The flexible curtain has flapssuch that it opens partially when the endoscope is inserted, and evenenables the physician to maneuver the endoscope around while feeding itinto the patient's esophagus, but still maintains a largely closed oralcavity volume. A small hole is preferably provided in this flexiblecurtain so that the subject's oral breathing can continue, largelythrough this hole The closed oral cavity volume prevents excess mixingof the exhaled breath stream with air from outside the mouth, such thatcapnographic sampling can be accurately performed on undiluted breath asit is exhaled. Furthermore, the hole in the flexible curtain ispreferably located close to the sampling opening in the roof of the biteblock, such that the capnographic measurement is performed on anaccurately representative sample of the exhaled and inhaled breathstream. In the capnographic bite block according to this preferredembodiment, the operation of the small hole and the sampling openingdisposed close to it can be readily understood by considering theseelements to be comparable to the effect of normal oral breath samplingwithout the use of a bite block. in this situation, the breath passingin and out of the large oral cavity, is sampled by the oral prong as itpasses in a stream through the small opening of the subject's lips—atleast in comparison to the cross sectional area of the mouth. Likewisewith the capnographic bite block of the present invention, the breathpassing in and out of the large combined internal volume of the oralcavity and the bite block is sampled by the sampling opening as itpasses in a stream through the small hole in the flexible curtain. Thebite block thus enables more efficient and accurate capnographicsampling than with prior art bite blocks under conditions of wide-openmouth breathing, which is common in endoscopic procedures.

Additional advantages of bite blocks according to the various preferredembodiments of the present invention, arise as a result of their correctand stable positioning within the mouth of the subject. When the biteblock has an incorporated breath sampling cannula or a gas deliverysystem, or both, then the stability of the positioning of the bite blockof the present invention in the user's mouth ensures that the desiredbreath sampling point or points, or the desired gas delivery point orpoints, are maintained during the procedure, and the tendency for thesubject to push out or move the bite block, which would misplace thesampling or delivery ports, is significantly reduced in comparison withprior art bite blocks. Additionally, when a separate oral/nasal cannulais used the firm placement of the subject's lips against the front plateof the bite block of the present invention assists in keeping the oralprong in its correct location sandwiched between the front plate and thesubject's upper lip.

There is therefore provided, in accordance with a preferred embodimentof the present invention, an endoscopic bite block, comprising:

-   -   (i) a tubular body comprising an inner end section adapted for        insertion into the mouth of a subject, an outer end section        adapted for insertion of an endoscopic probe, a central channel,        an upper wall having an upper outer surface, and a lower wall        having a lower outer surface,    -   (ii) a front plate connected to the outer end section of the        tubular body,    -   (iii) teeth positioning regions across at least part of the        upper and lower outer surfaces, the teeth positioning region in        the upper surface being disposed outwardly relative to the teeth        positioning region in the lower surface. At least one of the        upper and lower surfaces preferably has a generally flattened        portion on which its associated teeth positioning region is        disposed. Additionally, at least one of the teeth positioning        regions is preferably curved in the plane of its associated        surface to approximate the curve of the teeth in a human jaw. In        accordance with more preferred embodiments of the present        invention, in the above described bite block, at least one of        the teeth positioning regions may be a groove in its associated        surface, or a lowered platform region in its associated surface.

Additionally and preferably, the front plate of the bite block has itsupper section disposed outwardly relative to its lower section. The biteblock also preferably comprise connecting points for attaching the biteblock to the subject, and the connecting points are preferably locatedabove the horizontal center line of the bite block.

There is further provided in accordance with still another preferredembodiment of the present invention, a bite block as described above,and also comprising at least one of a gas collecting cannula and a gasdelivery cannula, or at least one nasal prong for delivery of gas to thesubject. The gas collecting cannula preferably comprises at least one ofnasal prongs and an oral collection channel, and in this case, the oralcollection channel is preferably disposed in the upper wall such that itenters the central channel in a direction facing the stream of exhaledoral breath. In the above described bite block, the gas delivery cannulapreferably comprises at least one of nasal and oral outlets.

In accordance with yet a further preferred embodiment of the presentinvention, there is also provided an endoscopic bite block, comprising:

-   -   (i) a tubular body comprising an inner end section adapted for        insertion into the mouth of a subject, an outer end section        adapted for insertion of an endoscopic probe, and a central        channel, the tubular body having at least one sampling opening        in fluid contact with the central channel,    -   (ii) a front plate connected to the outer end section of the        tubular body, and    -   (iii) a penetrable curtain disposed in the outer end section        across the majority of the internal cross section of the tubular        body and substantially preventing flow of gases across the        majority of the cross section of the tubular body. The        penetrable curtain is preferably such that an open area is        provided for passage of the orally inhaled and exhaled breath of        the subject. The open area is preferably disposed close to the        at least one sampling opening, such that the at least one        sampling opening samples substantially only the inhaled and        exhaled breath of the subject flowing within the tubular body.        Preferably, the open area is either a hole in the penetrable        curtain, or a gap at an extremity of the curtain. In accordance        with yet a further preferred embodiment of the present        invention, the penetrable curtain comprises flaps of material        peripherally secured to the tubular body.

There is even further provided in accordance with another preferredembodiment of the present invention, an endoscopic bite block asdescribed above, with a penetrable curtain, and wherein the curtain ispenetrable by the endoscopic probe such that the majority of the crosssection of the tubular body remains substantially closed of to thepassage of gases even when the endoscopic probe is maneuvered within thebite block.

In any of the above described bite blocks with a curtain, the curtain isprefer-ably constructed of a transparent material such that visibilityinto the oral cavity of the subject is maintained.

Furthermore, in accordance with yet another preferred embodiment of thepresent invention, there is provided an endoscopic bite block asdescribed above with a penetrable curtain, and wherein the samplingopening is connected to an internal sampling passage built into the biteblock, such that exhaled breath in the central channel can pass into theinternal sampling channel,

There is also provided in accordance with a further preferred embodimentof the present invention, an endoscopic bite block as described abovewith a penetrable curtain, and also comprising a recessed groove in theupper section of the front plate, and terminating close to the samplingopening, the recessed groove being adapted to receive the oral prong ofan oral/nasal cannula. In such embodiments, samples of the inhaled andexhaled breath from the tubular body pass into the oral prong when theprong is inserted into the recessed groove. Furthermore, the oral prongis preferably firmly held in the grooved recess between the front plateand the upper lip of the subject when the endoscopic bite block isinserted into the mouth of the subject. Any of the above describedendoscopic bite blocks having a curtain, may also preferably comprise atubular passage leading upwards from the sampling opening, the tubularpassage being adapted to receive the oral prong of an oral/nasalcannula. In such a case, samples of the inhaled and exhaled breath fromthe tubular body pass into the oral prong when the prong is insertedinto the tubular passage.

In accordance with yet more preferred embodiments of the presentinvention, there is provided an endoscopic bite block with a penetrablecurtain as described above, wherein the tubular body also comprises anupper wall having an upper outer surface, and a lower wall having alower outer surface, the endoscopic bite block also comprising teethpositioning regions across at least part of the upper and the lowerouter surfaces, the teeth positioning region in the upper surface beingdisposed outwardly relative to the teeth positioning region in the lowersurface.

At least one of the upper and lower surfaces preferably has a generallyflattened portion on which its associated teeth positioning region isdisposed. Additionally, at least one of the teeth positioning regions ispreferably curved in the plane of its associated surface to approximatethe curve of the teeth in a human jaw. In accordance with more preferredembodiments of the present invention, in the above described bite block,at least one of the teeth positioning regions may be a groove in itsassociated surface, or a lowered platform region in its associatedsurface. Additionally and preferably, the front plate of the bite blockhas its upper section disposed outwardly relative to its lower section.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 is a schematic illustration of a prior art endoscopic bite block;

FIGS. 2A to 2C are cut-away, cross-sectional, schematic views ofendoscopic bite blocks, constructed and operative according to preferredembodiments of the present invention;

FIG. 3 is an isometric schematic drawing of a bite block, according toanother preferred embodiment of the present invention, with integraloral-nasal cannula for oxygen delivery and for oral/nasal breathsampling, and also illustrating the various structural parts of the biteblock, shown in the cut-away sectional view of FIG. 2B;

FIG. 4 is a cross-sectional drawing of the bite block of FIG. 3, toillustrate the way in which the oral breath monitoring is performed;

FIG. 5 is a schematic isometric view of another endoscopic bite block,constructed and operative according to a further preferred embodiment ofthe present invention, intended for use with a separate oral/nasalcannula;

FIG. 6 is a schematic drawing of the bite block of FIG. 5, cut-away downits center line to show a preferred embodiment of the oral breathdirecting scoop; and

FIG. 7 is a view from the front of the bite block of FIG. 5, toillustrate a preferred shape of a closure curtain at its front end,according to a further preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1, which illustrates schematically a priorart endoscopic bite block, such as that described in the above-mentionedU.S. Pat. No. 5,174,284. The bite block has an internal channel 10, withupper surface 12 and lower surface 14 inclined towards the front of thebite block, where the front plate 16 is connected. As the subject'steeth 18, 20, close, the bite block is pulled into the mouth in thedirection 21 by the action of the teeth on the inclined upper 12 andlower 14 surfaces, so that the font plate moves from its initialposition 16, until it is lodged firmly up against the subject's lips 22,24, in position 16 a. At the same time, the tongue depressor 26 firmlygrips the subject's tongue 28, preventing it from moving.

However, the structure of the human mouth is such that the teethpositions are unlike those shown in the prior art drawing of FIG. 1, inthat the upper and lower teeth do not close naturally onto each other,as shown in FIG. 1. The upper jaw and teeth protrude further out fromthe skull than the lower jaw and teeth. When the human mouth is closed,the jaw morphology naturally causes the upper row of teeth to sit on thelower row at a position forward of the line of the teeth of the lowerrow. This natural rest position is further facilitated since the curveof the upper jaw teeth has a slightly larger radius than that of thelower jaw teeth. Gripping the bite block of FIG. 1 with the teethaligned opposite each other, as shown in FIG. 1, is only made possibleby pushing the lower jaw forward from its natural rest position. Whensuch a position is held for more than a short time, muscular tension andfatigue readily set in, causing unnecessary discomfort to the subject,in a situation where muscular relaxation is of great importance. Thisdiscomfort itself then also generates the urge to move or eject the biteblock, using the teeth or tongue. Furthermore, the unnatural position ofthe lower jaw tends to cause mouth movements, which are operative totilt the bite block from, its desired position. Such a tilted position,not having a well-defined seated location within the mouth, alsogenerates a lack of support and comfort to the subject, in a situationwhere both are important to ensure optimum subject tolerance of the biteblock and the endoscopic procedure. On the other hand, if the subjectgrips the bite block with his teeth in their natural rest position, withthe upper teeth forward of the lower teeth, then this naturally restfulposition of the jaw assists in avoiding the generation of moments whichmay tend to rotate the bite block from its optimum position.

Reference is now made to FIG. 2A, which is a cut-away, cross-sectionalschematic view of an endoscopic bite block 30, constructed and operativeaccording to a first preferred embodiment of the present invention. Theouter upper and lower surfaces 32, 34, of the bite block channel 36preferably have grooves positioned according to the approximate positionof the teeth in the upper jaw and the lower jaw. The top groove 38 forthe top teeth is set slightly forward of the lower groove 40 for theteeth of the lower jaw. The grooves are also preferably curved toapproximate the shape of the curve of the tooth line, being of largercurvature for the upper row than for the lower row. The regions wherethe subject's teeth can hold the bite block are therefore uniquelydefined such that the subject keeps the teeth of his upper jaw forwardof those of the lower jaw. The barrel of the bite block is thus heldfirmly between the teeth with a more natural feeling to the subject, andwithout the subject's jaws being constrained into a non-restfulposition.

Additionally and preferably, the front plate 42 at the top of the biteblock barrel is disposed further forward than the front plate 44 at thebottom of the barrel, to permit both the top lip regions of the subjectand his/her bottom lip regions to fit appropriately against both partsof the front plate. This assists in inducing the subject to grip thebite block naturally, also causing it to lie firmly, upright andcomfortably in the mouth.

Reference is now made to FIG. 28, which illustrates a cut-away,cross-sectional schematic view of an endoscopic bite block 31,constructed and operative according to another preferred embodiment ofthe present invention. The bite block is similar to that shown in FIG.2A, except that instead of having grooves for the teeth in the top andbottom surfaces of the barrel, a lowered platform region 39 is providedin the top surface. This has the effect of constraining the subject'steeth less rigorously than the grooved embodiment of FIG. 2A, thereforeproviding a more comfortable gripping position, and especially fordifferent subjects with slightly different shaped teeth curves andpositions. Additionally and preferably, on the bottom surface 34, thereis provided a sloping stepped depression 41, set further back than theedge of the lowered platform region of the upper surface, which alsoenables more flexibility in teeth positioning for the lower jaw teethalso.

Reference is now made to FIG. 2C, which is a view from above, alongsection IIC-IIC of FIG. 2B, showing how the edge 43 of the loweredplatform region 39 is curved to shape the approximate curve of thesubject's upper teeth.

In any of the preferred embodiments shown in FIGS. 2A to 2C, the groovesor lowered regions may preferably be fined with a material softer thanthat of the body of the bite block, such that the grip of the bite blockis made to be more comfortable. Alternatively and preferably, thedefining regions for the teeth may be at the same height as the rest ofthe surface in which they are incorporated, but may be made of softer orharder material to define the teeth gripping positions. Alternatively,even the raised section 32 of FIGS. 2B and 2C may be made of softermaterial to provide for increased user comfort.

The essence of all of these embodiments of the present invention,whether similar to those shown in FIGS. 2A to 2C or not, is that theteeth be directed, by means of a distinctive defining region of thesurface, to grip the bite block with the subject's jaws in a naturalposition and hence in a more relaxed manner. According to differentpreferred embodiments, this defining region may be of different height,texture, material, or combinations thereof, so long as it adequatelyfulfils its function of directing the teeth to bite the block with anatural and as relaxed as possible, jaw position.

Reference is now made to FIG. 3, which is an isometric schematic drawingof a bite block, according to another preferred embodiment of thepresent invention, taken from the rear, to illustrate the variousstructural parts of the bite block shown in the cut-away sectional viewof FIGS. 2B and 2C. The various features of FIG. 3 are denoted by thesame reference characters as those of FIGS. 2B and 2C. The bite blockshown in FIG. 3 differs from those in FIGS. 2A to 2C in that it alsoincorporates cannulae, both for sampling the subject's breath, and forsupplying gas to the subject, as will be discussed hereinbelow. However,the structural features relating to the location of the bite block inthe subject's mouth are essentially those of FIGS. 2B and 2C, and thesefeatures are now explained.

In the three-dimensional representation shown in FIG. 3, in the uppersurface 32 of the tubular body, there is shown a curved lowered platformfor the upper teeth 39, whose rear edge 43 is designed to approximatelymatch the curvature of the upper teeth of a human jaw. In the lowerouter surface of the tubular body, there is seen a sloping steppeddepression 41, set further back than the edge 43 of the lowered platformregion of the upper surface, as described hereinabove.

FIG. 3 also illustrates how the bite block of the present invention ispreferably attached to the subject's head. Bite blocks generally havelugs or attachment points at the outer edges of the front plate forconnecting a band to the front plate to hold the bite block firmly inposition against the subject's lips. In prior art bite blocks, theselugs or attachment points are generally located at the center of theheight of the front plate, in line with the center line of the bore ofthe barrel. in FIG. 3, the lugs or attachment points 46, according tothis preferred embodiment of the present invention, are located abovethe center of the height of the front plate, such that the pull of theattaching band tends to exert a stronger pull to the top of the frontplate than to the bottom of the front plate, thus assisting to overcomeany moment generated by the teeth tending to tilt the bite blockoutwards, and keeping the bite block seated firmly and upright in thesubject's mouth. However, since there may also be a tendency for thesubject, to push the bite block out from the bottom with his tongue,which would be assisted by a high attachment, the position of theattachment has to be determined by experience with the actual design ofthe bite block.

In addition to increasing the comfort and tolerance of the subject tothe very presence of the bite block in his mouth during an endoscopicprocedure, when a nasal or an oral-nasal cannula for sampling breath orfor delivering gas is incorporated into the bite block of the presentinvention, it is possible to reduce some of the problems of prior artbite blocks with incorporated gas delivery cannulae, or as used withseparate sampling cannuale.

Reference is now made again to FIG. 3, to those aspects of the biteblock of the present invention relating to the integration of an oral,or a nasal or an oral-nasal cannula for breath sampling, and of anintegral gas delivery system, which can he used to supply supplementaloxygen to the subject, generally through a nasal delivery outlet oroutlets. The preferred embodiment of the integral bite block/cannulacombination shown in FIG. 3 shows an oxygen delivery outlet 52, fed bymeans of an oxygen supply nipple 54. The delivery outlet 52 should bemaintained below the subject's nostrils to provide an effective supplyof supplemental oxygen. An internal channel, unseen in FIG. 3, andconnected to the delivery nipple, can also supply oxygen to thesubject's mouth through the channel of the bite block, if such an optionis used. in addition, the bite block of FIG. 3 also shows a pair ofnasal prongs 56, 58, preferably operative for the collection of exhaledbreath for capnographic monitoring of the subject during the procedure.The exhaled breath is preferably passed to a capnographic monitorthrough the breath collection tube 60. A sampling channel, unseen inFIG. 3 and connected to the collection tube 60, can also be used tosample the orally exhaled breath of the subject from the channel 36 ofthe bite block. As it is usual for endoscopic procedures to be carriedout with the subject lying on the left side, the oxygen delivery nipple54 and the breath collection tube 60 are preferably located on the righthand side of the bite block.

The novel structural features of the bite block of the above-describedpreferred embodiments of the present invention, namely the offset teethpositioning regions, the staggered front plate and the attachment lugspositioned above the bite block center line, encourage the maintenanceof the bite block in a predetermined, upright, position within the mouthof the subject, and thus enhance the correct positioning of the breathsampling prongs and/or of the gas delivery outlets, relative to thesubject's nostrils and/or mouth, whichever are appropriate. The biteblock, according to these additional preferred embodiments of thepresent invention, thus also provides for correct positioning in themouth, both for efficient oxygen delivery and for accurate breathsampling.

Reference is now made to FIG. 4, which is a cross-sectional drawing ofthe endoscopic bite block of FIG. 3, viewed along the plane marked A-Ain FIG. 3, to illustrate the way in which the oral breath monitoring isaccomplished. The body of the capnographic bite block has an oral breathsampling channel 62 built into the roof of the central channel. Part ofthe exhaled oral breath flowing in the central channel 36 of thecapnographic bite block flows into this sampling channel, and iscollected by the collection tube 60 for transfer to the capnographicmonitor, together with the nasal exhaled breath collected through thenasal prongs 56, 58. Flow of exhaled breath into the sampling channel isaided by the shape of the central roof, in which the entry port of thesampling channel is preferably positioned jutting out of the roof in ascoop configuration, such that it readily intercepts part of the exhaledbreath flow.

Reference is now made to FIG. 5, which is a schematic isometric viewfrom the rear of another capnographic bite block 66, constructed andoperative according to a further preferred embodiment of the presentinvention. The bite block is intended for use with a separate oral/nasalcannula, such as that described, in the above-mentioned U.S. Pat. No.6,422,240. The subject preferably puts on the cannula before the biteblock is inserted into the subject's mouth, and it is operated as astandard sampling and delivery cannula. The bite block 66 has an opening68 in the roof of the channel 36, extending into the channel, and theend of the oral sampling prong 70 of the cannula is arranged toterminate close to this opening, or even to just project into thisopening such that its tip just projects into the top of the channel. Inthis position, the oral prong is able to sample the orally exhaledbreath stream without being disturbed by, and without disturbing, theinsertion of the endoscopic probe through the bite block. In order toincrease the collection efficiency of the oral sampling prong, the pointat which the opening breaks through into the central channel canpreferably be provided with a small scoop, not visible in the drawing ofFIG. 5, though shown below in FIG. 6, and directed inwards into thedirection of the subject's mouth, such that it samples the breath streammore effectively. The wall of the tip of the oral prong 70 in thedirection of the subject's mouth is preferably cut away, leaving thewall at the front of the prong end intact to intercept the oral breathflow more efficiently. Furthermore, since the bite block of the presentinvention enables use of the same cannula both before, during and afterthe bite block is in the subject's mouth, this cut-away tip is usefulfor ensuring efficient interception and sampling of the exhaled breatheven without the bite block. Such a cut away tip has a further function,as will be described hereinbelow in relation to the details shown inFIG. 6.

According to a further preferred embodiment of the present invention, agroove or recess 72 is provided in the center of the top of the frontplate of the bite block, in which the oral probe sits when the biteblock is inserted in place in the subject's mouth. In practice, the biteblack can be simply placed straight into the mouth of the subject, overthe oral prong, and the front plate is operative to hold the oral prongsnuggly within the recess, thus ensuring the stability of its desiredsampling position within the opening. In this respect, the otherabove-described features of the bite block of the present invention,which contribute to the comfort and accuracy of the positioning of thebite block within the mouth and against the subject's lips, also ensurethat the oral probe is held positively in its desired sampling positionwithin the groove in the front plate. The groove is also operative tocompensate for slight differences in the size of the facial features ofthe subject, since when the oral probe is tightly held in the groovebetween the groove and the subject's upper lip, even if the tip of theoral prong does not reach its optimal position near the bottom of thegroove, the groove conducts the sampled breath from the sampling openingto the end of the oral prong.

The bite block of FIG. 5 has slightly different design features for theteeth positioning features to those shown in FIGS. 2A to 3, but thefunctional purpose and result is identical.

It is important that, in those embodiments where a scoop is notprovided, the end of the cannula just reaches its predefined positionclose to the roof of the central channel of the bite block, withoutprotruding into the central channel too much, and without falling shortthereof too much. This condition should preferably be achievedindependently of the different height of the upper lip dimension ofdifferent subjects. In order to ensure this, according to furtherpreferred embodiments of the present invention, the oral prong of thecannula can preferably be provided with an adjustable sliding sectionenabling the effective length of the oral prong to be adjusted to suitthe subject's facial features. This enables compensation to be made forthe different position acquired by the end of the oral prong before andafter inserting the bite block, when the position of the tip wouldchange relative to the mouth because of the wide opening needed with thebite block inserted.

Alternatively and preferably, a cannula with a fixed oral prong could beused, and the opening in the roof of the bite block provided with atubular chimney at its top end, into which the oral prong of the cannulais threaded. The length of the oral prong is selected such that the endof the oral prong is always situated within the chimney, regardless ofdifferences in the size of the facial features of the subject Accordingto this embodiment, the oral prong should fit into the tubular chimneywithout an excessive gap, so that excessive leakage or dilution of thesampled gas is prevented. The use of the recessed groove embodimentthough, may in many situations be more advantageous than the chimneyembodiment, since the former more readily enables a cannula with astandard length oral prong to be used, such that the same cannula can beused by the subject both before, during and after the bite block hasbeen used.

Reference is now made to FIG. 6, which is a schematic drawing of thebite block of FIG. 5, cut-away down its centerline to show a preferredembodiment of the oral breath directing scoop 74 at the bottom of thegroove 72 the oral sampling prong of the cannula. The thin spoon shapeof the scoop effectively becomes the roof of the central channel,separating between the endoscope probe and the oral prong. Using thisembodiment, the base of the scoop prevents the oral prong fromprotruding into the channel too much and from being occluded or moved bythe endoscope probe. The cut-away tip of the oral probe, as shown inFIG. 5, is also important to prevent the end of the oral probe frombeing blocked if the tip is inserted to the floor of the scoop.

At the front end of the bite block shown in FIG. 5, there is shown anadditional feature 76, according to a further preferred embodiment ofthe bite block of the present invention, which attempts to solve theproblem of efficient capnographic sampling in the situation when openmouth breathing is the main form of breathing being done by the subject.The cross sectional area of the bite block inner channel 36 is generallyclosed off near its outer end, forward of the plane of the oral samplingprobe opening 68, by means of a flexible curtain 76, composed of flaps,so as to generate an inner volume in the inside of the bite block,substantially isolated from the external air, except for a small holethrough which the subject inhales and exhales and at which the inhaledand exhaled breath stream can sampled. The flexible curtain flaps arepreferably made of a thin plastic material, selected to be of thecorrect thickness that they maintain their position when undisturbed,yet bend readily when pushed by the endoscope probe, thus not limitingthe endoscope maneuvers. The plastic material is also preferablytransparent so that the physician can see inside the oral cavity whilehe is inserting and maneuvering the endoscope probe.

Reference is now made to FIG. 7, which is a view from the front of thebite block 66 of FIG. 5, to illustrate a preferred shape of the plasticcurtain 76 and its flaps. The curtain is preferably attached to thefront plate of the bite block around its periphery 78, and the flaps arepreferably formed by means of slits 80 across the surface of thecurtain, from the periphery towards a point within its cross section, sothat the flaps open without hindrance when an endoscopic probe isinserted into the bite block. However, the flaps pushed aside by theendoscopic probe close back around the probe once it has been inserted,and thus still maintain a largely closed oral cavity volume, from whichcapnographic sampling can be performed accurately. in the preferredembodiment shown in FIG. 7, the vertex of the flap structure is shownnear the top of the cross section of the bite block channel, but it isto be understood that the slits can be provided in any form which allowseasy bending and effective sealing once the endoscopic probe has beeninserted into the bite block. A small hole 82 is also preferablyprovided in the slit curtain to enable easy expulsion and inhalation ofthe subject's breaths. This hole is preferably placed close to thesampling opening in the roof of the central channel, so that the flowpassing the opening has good inhalation and exhalation exchangeattributes. Under these conditions, the samples collected for thecapnographic analysis are authentic samples of the exhaled and inhaledbreath of the subject. Additionally, because of the isolated volumewithin the bite block, which is operative to direct and concentrate thebreath sample, both pressure and flow wise towards the breathing hole,which is the only substantial exit, and to isolate it from the outside,the sample is substantially undiluted by extraneous air duringexhalation. The accuracy of the capnographic measurement is thereforegood.

The various features of the bite block of the present invention include,inter alia, teeth positioning features, front plate alignment, attachingband positions, openings for using the oral prong of separate oral/nasalcannulae, blocking curtain flaps for closing off the internal volume ofthe bite block, and others. It is to be understood that this inventionis not meant to be limited to the specific combinations of featuresdescribed in the preferred embodiments described above in thisapplication, but rather that any combination of the various features ofthe preferred embodiments described can be used in one endoscopic biteblock, or any feature can even be used separately in a bite block,thereby providing the individual advantages of that feature to the biteblock.

It is appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the present inventionincludes both combinations and subcombinations of various featuresdescribed hereinabove as well as variations and modifications theretowhich would occur to a person of skill in the art upon reading the abovedescription and which are not in the prior art.

1-32. (canceled)
 33. An endoscopic bite block, comprising: a centralchannel comprising an upper wall having an upper outer surface and anupper inner surface; and a lower wall having a lower outer surface and alower inner surface; a breath sampling channel configured to sampleorally exhaled breath; a front plate merged with an outer end section ofsaid central channel, said front plate comprising an upper section and alower section; said upper section comprising a groove, wherein at leastpart of a wall of said groove is common with a wall of said uppersection of said front plate; and a collection tube connectable to saidbreath sampling channel, said collection tube configured to receive theorally exhaled breath sampled by said breath sampling channel.
 34. Theendoscopic bite block according to claim 33, wherein at least part ofsaid upper and lower outer surfaces of said central channel comprise amaterial softer than that of said upper and lower inner surfaces. 35.The endoscopic bite block according to claim 33, wherein said collectiontube is disposed in said upper wall of said central channel, such thatit enters said breath sampling channel in a direction facing a stream ofexhaled oral breath.
 36. The endoscopic bite block according to claim33, wherein at least one of said upper and lower outer surfaces has agenerally flattened portion.
 37. The endoscopic bite block according toclaim 33, wherein at least one of said upper and lower outer surfaces iscurved to accommodate a human jaw.
 38. The endoscopic bite blockaccording to claim 33, wherein said front plate further comprisesconnecting points for attaching said bite block to said subject, saidconnecting points located above a horizontal center line of said biteblock.
 39. The endoscopic bite block according to claim 33, furthercomprising a penetrable curtain disposed in said outer end section ofsaid central channel across a majority of an internal cross section ofsaid central channel thereby substantially preventing flow of gasesacross said majority of said cross section.
 40. The endoscopic biteblock according to claim 33, wherein said collection tube is furtherconfigured to receive nasal exhaled breath from nasal prongs receivedwithin said groove.
 41. The endoscopic bite block according to claim 33,wherein said front plate further comprises at least two lateralopenings, wherein each of said at least two lateral openings areconfigured to be positioned on opposite sides of the patient's mouth,thereby reducing a contact area of said front plate with said subject'sskin.
 42. The endoscopic bite block according to claim 33, wherein saidupper section of said front plate is disposed forwardly relative to saidlower section of said front plate.
 43. The endoscopic bite blockaccording to claim 33, wherein said groove is formed within a wall ofsaid upper section, such that said wall of said upper sectioncircumferentially delimits said groove.